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Sunday, January 27, 2013

Misconceptions about the Anthropic Principle

I keep coming across statements about the anthropic principle leaving its mark on physics that strike me as ill-informed, most recently in a book I am presently reading “The Edge of Physics” by Anil Ananthaswamy:

“The anthropic principle – the idea that our universe has the properties it does because we are here to say so and that if it were any different, we wouldn’t be around commenting on it – infuriates many physicists, including [Marc Davis from UC Berkeley]. It smacks of defeatism, as if we were acknowledging that we could not explain the universe from first principles. It also appears unscientific. For how do you verify the multiverse? Moreover, the anthropic principle is a tautology. “I think this explanation is ridiculous. Anthropic principle… bah,” said Davis. “I’m hoping they are wrong [about the multiverse] and that there is a better explanation.””

The anthropic principle has been employed in physics as a proposed explanation for the values of parameters in our theories. I’m no fan of the anthropic principle because I don’t think it will lead to big insights. But it’s neither useless nor a tautology nor does it acknowledge that the universe can’t be explained from first principles.

The anthropic principle doesn’t necessarily have something to do with the multiverse.

The anthropic principle is true regardless of whether there is a multiverse or not and regardless of what fundamentally is the correct explanation for the values of parameters in our theories. The reason it is often mentioned in combination with the multiverse is that proponents of the multiverse argue it is the only explanation, and no further explanation is needed or necessary to look for.

The anthropic principle most likely cannot explain the values of all parameters in our theories.

The anthropic principle might however still work for some parameters if their effect is almost independent on what the other parameters do.

The anthropic principle is trivial, but that doesn’t mean it’s useless.

Mathematical theorems, lemmas and corollaries are results of derivations following from assumptions and definitions. They essentially are the assumptions, just expressed differently, always true and sometimes trivial. But often, they are surprising and far from obvious, though that is inevitably a subjective statement. Complaining that something is trivial is like saying “It’s just sound waves” and referring to everything from engine noise to Mozart.

And so, while the anthropic principle might strike you as somewhat silly and trivially true, it can be useful for example to rule out values of certain parameters of our theories can have. The most prominent example is probably the cosmological constant which, if it was too large, wouldn’t allow the formation of structures large enough to support life. This is not an empty conclusion. It’s akin to me seeing you drive to work by car every morning and concluding you must be old enough to have a driver’s license. (You might just be stubbornly disobeying laws, but the universe can’t do that.) Though, this probably doesn’t work for all parameters, see 2.

The anthropic principle does not imply a causal relation.

Though “because” suggests so there’s no causation in the anthropic principle. An everyday example for “because” not implying an actual cause: I know you’re sick because you’ve got a cough and a runny nose. This doesn’t mean the runny nose caused you to be sick. Instead, it was probably some virus. Alas, you can carry a virus without showing symptoms so it’s not like the virus is the actual “cause” of my knowing. Likewise, that there is somebody here to observe the universe did not cause a life-friendly universe into existence. (And the return, that a life-friendly universe caused our existence isn’t the case because life-friendly doesn’t mean interested in science, see 3. Besides this, it’s not like the life-friendly universe sat somewhere out there and then decided to come into existence to produce some humans.)

The applications of the anthropic principle in physics have actually nothing to do with life.

As Lee Smolin likes to point out, the mentioning of “life” in the anthropic principle is entirely superfluous verbal baggage (my words, not his). Physicists don’t usually have a lot of business with the science of self-aware conscious beings. They talk about formation of large scale structures or atoms. Don’t even expect large molecules. However, talking about “life” is arguably catchier.

The anthropic principle is not a tautology in the rhetorical sense.

It does not use different words to say the same thing: A universe might be hospitable to life and yet life might not feel like coming to the party, or none of that life might ever ask a why-question. In other words, getting the parameters right is a necessary but not a sufficient condition for the evolution of intelligent life. The rhetorically tautological version would be “Since you are here asking why the universe is hospitable to life, life must have evolved in that universe that now asks why the universe is hospitable to life.” Which you can easily identify as rhetorical tautology because now it sounds entirely stupid.

It’s not a new or unique application.

Anthropic-type arguments, based on the observation that there exists somebody in this universe capable of making an observation, are not only used to explain free parameters in our theories. They sometimes appear as “physical” requirements. For example: we assume there are no negative energies because otherwise the vacuum would be unstable and we wouldn’t be here to worry about it. And requirements like locality, separation of scales, and well-defined initial value problems are essentially based on the observation that otherwise we wouldn’t be able to do any science, if there was anybody to do anything at all.

55 comments:

A nice synopsis respective of the confusion found to be rampant regarding this principle. How I’ve come to think of the Anthropic Principle and the debate which surrounds it being as simply an extension of the old "if a tree falls in the forest...." argument. As such I didn't see you mention that the principle is recognized as being presented with varying degrees of strengths to be considered; although what you've written in as much has that to gathered as such. Moreover the one that has many scientists and some philosophers cringe is the strong version of the principle, which suggests any universe, is compelled to have life to form as necessary in the context of it representative of reality. On the other hand the weak version has it that only in a universe capable of supporting life will there be beings capable of observing the fine tuning that's necessary. In the end for me it simply seems to boil down to what holds for people as to what's important, the forest, the falling tree or the one to hear it.

"Imagine a puddle waking up one morning and thinking, "This is an interesting world I find myself in — an interesting hole I find myself in — fits me rather neatly, doesn't it? In fact it fits me staggeringly well, must have been made to have me in it!" This is such a powerful idea that as the sun rises in the sky and the air heats up and as, gradually, the puddle gets smaller and smaller, it's still frantically hanging on to the notion that everything's going to be alright, because this world was meant to have him in it, was built to have him in it; so the moment he disappears catches him rather by surprise. I think this may be something we need to be on the watch out for. We all know that at some point in the future the Universe will come to an end and at some other point, considerably in advance from that but still not immediately pressing, the sun will explode. We feel there's plenty of time to worry about that, but on the other hand that's a very dangerous thing to say."

Do we have some testable predictions following from anthropic principle? I don't see any... IMO it's just a tool, which is helping the unfalsifiable theories (and their promoters) in easier survival, i.e. in similar way, like the religion. The God concept behaves in similar way: it serves only for postdictions, explanations - and excuses.

Anthropic principle is only (and even then barely) meaningful in the context of a multiverse because only if we have an ensemble of universes with all possible parameter values it makes sense to say that we observers must find ourselves in the habitable one. But of course that hardly explains anything because it introduces the whole nonsense of the multiverse. So it's like explaining where the universe came from by postulating god/creator. No rational person can ever consider such an explanation satisfactory.

In the case where there is only one universe with one particular set of parameter values the principle doesn't explain anything and is completely absurd unless you buy into some metaphysical nonsense that universe is somehow compelled to produce intelligent life.

Your example of cosmological constant makes just such an assumption: "cosmological constant which, if it was too large, wouldn’t allow the formation of structures large enough to support life." Well the universe or the cosmological constant couldn't give a damn if they could or could not support life cause they are not alive and don't share our concerns.

The value of cc is what we measure it to be and that is all that can be meaningfully said about it currently.

to me it always seems that in theoretical or fundamental physics at least, the anthropic principle is invoked as a copout to avoid the immensly difficult task of narrowing down the landscape (of solutions of the dynamic equations) to the part which potentially describes the universe as we observe it, by aproppriate physical and mathematical reasoning.

It seems like throwing in the towel ...

In addition, I've heard arguments that invoking the holographic principle, it is physically not meaningful to ask what is outside our universe or talking about the physical existance of any "multiverse".

However some applications in other contexts you discribe were interesting to read and seem not too bad :-)

The anthropic universe is the usual Freudian shtick writ large. That we are not being plundered, enslaved, and eaten by neighbors is rather disappointing; so we do it to ourselves.

What is a bonafide nice place for intelligence, not merely life? A star that calmly sustains a few billion years. A wet planet between -30 and 110 C, with a magnetic field to shield it against stellar wind stripping volatiles. Not too much gravity so as to allow leaving (and walking in a forest). Tides are useful - and a big moon stabilizes the planetary rotation axis against mass redistribution. Societies without optical glass miss microscopes, corrective lenses, and telescopes (mirrors are not enough). Fossil fuels are a huge boost while they last. One despairs of a universe whose few societies are no more evolved than Laureti's ""Triumph of Christianity".

You wrote: "For example: we assume there are no negative energies because otherwise the vacuum would be unstable and we wouldn’t be here to worry about it."

Since I always learn something by disagreeing with you, here goes:

Dirac did not assume that there are no negative energies, instead he filled the negative-energy sea. In general, we try to make our mathematical equations intelligible, and not solely because of the anthropic principle.

I think it is an important distinction, given that ideas like that of Tegmark are floating out there. We have to "prune" our mathematical objects considerably in order to make them into a description of reality. I'd really say that negative energies, anomalies, non-decoupled tachyons, runaway solutions, etc., are somehow "natural" in mathematics, it is our "pruning" that makes mathematics suitable for doing physics.

While there is the unreasonable effectiveness of mathematics in doing physics, there is also a great deal of superfluous baggage that mathematics carries, and a difficulty we have in constructing physical theories from mathematics is figuring out how to discard this baggage. In trying to do so, until String Theory, I don't think we invoked the anthropic principle.

Trivial? There is a story about a mathematician, maybe Hardy, who was demonstrating a proof on a blackboard. At one point, he said "this is trivial" then paused a bit. Then he stepped back from the blackboard. Then he sat down for half an hour in silent thought. Then he returned to his lecture and continueed with "Yes, it is trivial."

Everything you wanted to know about the anthropic principle: check out the book The Anthropic Cosmological Principle by Barrow and Tipler. (Note, I don't necessarily agree with everything in this book, though it is well written and researched. Tipler, of course, later went off the deep end.)

At least half of the confusion about the anthropic principle arises because people misunderstand the way "because" is used when discussing it.

As Max Tegmark points out, the multiverse is not some deus ex machina invoked to explain the inexplicable, but rather a prediction of certain theories. Yes, Robert, a testable prediction. (And it has nothing to do with WIMPs.)

There is a quite famous example of a confirmed prediction using the anthropic principle: Hoyle used it to predict certain energy levels in the carbon-12 nucleus.

The multiverse and the anthropic principle are often discussed together, but there are aspects of the multiverse apart from the anthropic principle and vice versa.

Change "rhetoric" to "rhetorical". The former is the noun, the second the adjective. This is probably one of the most confusing points in English. Sometimes nouns and adjectives have the same form, but not here. Sometimes the two forms are both adjectives: there is electrical and electric, which have a different meaning (there is an electrical engineer, someone who as studied electrical engineering; an electric engineer would be a robot or something); there is elliptic and elliptical (one sees both); there is magnetic but not magnetical.

As I said, the use of the anthropic principle is to constrain the freedom in our theories. You could in principle use it to predict the range of some parameter, but I don't know of any example where this has been done for a parameter that wasn't already known anyway. Best,

I should have mentioned that my equivalent problem in German is al/ell. When does one say "real" and when "reell"? Formal vs. formell? Individual/individuell? Original/originell? In some cases it is a noun (or, perhaps, and adjective being used as a noun) vs. an adjective, e.g. "Das ist ein Original, aber nicht besonders originell." But that isn't always the case, e.g. formal and formell are, as far as I know, both always adjectives.

This books disagrees: http://link.springer.com/article/10.1007%2Fs00407-010-0068-8?LI=true but I think the disagreement is based on a misunderstanding. Google gives 81,600 hits for "Hoyle carbon resonance". I think that, in any meaningful sense, this is an example of a successful anthropic prediction.

As I said, the anthropic principle doesn't necessarily have something to do with the multiverse. It's a fact that you can use to constrain parameters even if you don't subscribe to the multiverse. No, you do not need an ensemble with universes with all possible values of parameters to make the statement that the parameters in our universe must be so that observers can exist. The latter is true regardless of whether the ensemble exists or not. The thing is just that if you believe in a multiverse, then the anthropic principle is more or less forced upon you as explanation why the combination of parameters that we observe, out of all possible, is so unlikely. Though, as you know, the devil is in the details, here the meaning of the little word "unlikely". Best,

Well, I've tried to keep it short. Yes, there are different variants of the anthropic principle. I previously wrote about the ones that I've encountered in physics in this earlier post. Yes, there's also the strong version. But I've never seen it appearing in physics. Best,

Yes, this right. I think it's also what Ananthaswamy was expressing in the quote above "It smacks of defeatism...". I think though one should at least consider the possibility that it might in fact be correct. Maybe there just is no better explanation. As I explained in this earlier post, the problem goes much deeper than the question about the values of parameters in our theories. Because even if you'd explain these, you'd still be left asking, well, why these theories. Why not some other. Why matter and space-time to begin with? Best,

I don't know if there is a rule! I once had a longer exchange with a Chinese postdoc about German classes she was taking, and she was explaining me lots of German grammar rules. Most of them I had never heard of! Eg, I never consciously noticed that words ending on "ung" are female. That having been said, my mom complains that my German seriously suffered from my moving around the Globe. So at this point I'm afraid I speak neither German nor English properly, so I appreciate your corrections even more :o) Best,

When I wrote negative energies I was actually referring to ghosts, not the Dirac sea, I was just trying to avoid terminology.

I don't think I actually disagree with you. Yes, there are physical assumptions that are not really of the anthropic type, in that they adapt a theory to our experience even though not adapting it doesn't necessarily say something about the existence of life. Eg, if you think of non-normalizable runaway solutions in quantum mechanics. You discard them not primarily because they'd prohibit the existence of life, but because they don't make any sense in the framework you're working with to begin with. You could say something similar about timelike closed curves, divergences/renormalization and probably many other examples.

What if someone, almost infinitely more intelligent than us, discovered a mathematical/logical formula describing everything that is in the universe we are inhabiting (and I am not referring to any god).

And then he built a computer to do the simulation. Wouldn't we find ourselves in the same situation discussing about anthropic principle.

Let's take backwards bit by bit:

Is _our_ reality dependent of the computer running. If the computer runs out of power in the middle of me writing this. I wouldn't notice it, of course.Then the computer gets a new battery, and can start simulation from last back-up point, our yesterday. It simulates up to this moment second time and continues forward.Do we notice being simulated twice? Surely not. Any number at least 1 is equally good.

But why 1, why not 0. If the formula is there, and the formula is self-consistent, without any randomness, is there any difference for our behavior between zero and one simulation rounds? Is it enough that the genius has invented the formula?

Accepting this leads to think why do we need that genius. Should it be enough that the formula is there to be discovered, without anyone discovering it.

So we could be hanging here just because _the_ formula exists in the formula-space. And we can do nothing to verify or falsify the statement.

The point being: Anthropic principle can only be used to point out phenomena we should stop studying, focusing on the ones we can verify.

@Arun, the language wherein it is best described how nature works, is mathematics. Nature does not care about what you or I like or not. So it is only natural that the more we learn about fundamental physics, the more mathematical the theories we use describe this, get.

Pleas stop trying to make people angry and start ugly flame wars about ST here, this is not constructive.

For clarification and critique about some different versions of the AP: the trivial circular form, that the universe's laws have to be consistent with our being here, is indeed rather trivial. Of course, outcomes are expected to be consistent with laws and initial conditions. The real question is, why did "the" (or "our" as may be) universe have these particular laws and ICs with the outcomes it had, instead of some other ICs and laws with alternate associated outcomes? And whether someone would be there to notice should be beside the point of a mature "realist" philosophy.

IOW, we are really asking, why1. IC_1 → outcome_1instead of2. IC_2 → outcome_2and so on.Also put as: "why is this possible universe (model world, "mathematical structure") etc actualized as "substantive" (whatever that really means!) and not just "math" (or is it just math?), whereas other PWs are "just math" as concepts we can imagine (a physical world with 13 space dimensions etc.) And please, don't anyone just use our physical laws to say why not, those are just *our* laws and an integral, defining feature *of* our universe - not something higher level like a logical necessity for all of them.

Some folks like Tegmark, the modal realists, get around this by saying: there is not difference, and all these "abstractions" are as real as any other, and ours is one such "mathematical structure"! I find that hard to beleive, just from the experience of "existing" etc. (now I've worked consciousness into it!)

But if MUH/MR is wrong, then we have to ask: why would the or a universe that "really exists" just happen to be life-friendly, if the "why" of it being that way is not specially designed for that? Why coincidentally such a luck break? And that isn't answered by fallacious circular appeal to the banality that outcomes must be consistent with beginnings, whether or not colyly done as if a reverse causation (fallacy of it *was* that way because we *are* here now) etc. BTW I'm not suggesting Bee made these mistakes, they're out there and need to be exposed.

As for attempts to explain why then, if not self-selection in a multiverse full of basically every possible world, does ours have the properties it does: there is no foundational way to do that, in principle, for the very reasons that stimulated people like Tegmark to believe in the MUH. Math doesn't come with an extra "ghost" tagging models with "deserves to be a real material world". There is not way to derive that extra feature, justify it, even *describe it* with logical methods, as the modal realists like David Lewis well argued. There are just "models", constructions that Platonically exist, and nothing more *in the math or the logic*. "Realness" of the extra sort we attribute to our world (maybe because we *feel alive*), our being sure it's "not just an abstraction", cannot be derived from the former. (If you think it can, then do it ...)

Hence, we need something *else* - like it or not - to impose selective substantiation upon the mindscape of model universes. And hence it is silly to say e.g. the cosmological constant or the fine structure constant "doesn't care" whether we are, or could be, here - you don't know what it comes from or why anymore than I or bible thumpers do. It is at least a striking thing, that something allegedly "without purpose" is finely tuned to produce life when it is such a tiny slice among model worlds. Note again, the circular argument can't explain it by the trick of pretending to reverse the cause and effect of our being here to wonder about it.

Ahh, indeed: "... as if we were acknowledging that we could not explain the universe from first principles." But that's just it. Like I explained, we *can't* explain the universe (this versus that) from first principles! That's what motivates people like Tegmark to the MUH, that all of the possible worlds exist.

Consider these four enigmas:1) Why is the spectrum of gauge groups in the SM as it is?2) Why is the mass spectrum in the SM as it is?3) Why is the spectrum of spin states as it is?4) Why is the spectrum of critical exponents in 2D critical phenomena as it is?

It has been suggested that the first two questions have anthropic answers. However, to me all four questions are very similar, and we know that the answer to the last two is not anthropic; they follow from the projective representations of SO(3) and the infinite conformal group, respectively. To me it is inconceivable that such similar questions don't have similar answers.

Bee: "No, you do not need an ensemble with universes with all possible values of parameters to make the statement that the parameters in our universe must be so that observers can exist. The latter is true regardless of whether the ensemble exists or not."

Your statement "that the parameters in our universe must be so that observers can exist," (which I never used), is ambiguous. It can be understood in 2 different ways:

1. Since we already know observers do exist the parameter values must be consistent with this fact.

2. Our universe could not have ended up with parameter values excluding observers.

The first interpretation makes the statement trivially true and uninteresting. It's simply a restatement of the fact that different observations we make must produce consistent results. You don't need to come up with anthropic principle to know that, it's the bedrock of scientific method.

The second meaning which I consider the proper anthropic principle is nonsensical to me. The fact that our universe does have observers certainly doesn't prove that parameter values excluding them were not possible.

The whole argument makes as much sense as arguing that since you rolled 6 on a dice only 6 was possible to begin with. Patently false.

And that is not the only problem, we certainly have no clue what parameter values lead to observers. We only know which values would exclude ourselves. It's possible and quite likely that there are plenty of other combinations which would lead to observers much superior to our meager selves.

Besides the term observer is ill defined anyway. For example a rock carved by the wind is an observer in that it forms an internal representation of external stimuli in the same way humans form such representations. It can also act on that representation just as humans do by cracking and falling apart. The only difference is complexity which is relative anyway.

PTMR, you misunderstand one of the AP versions you are apparently referring to when you write:

"The second meaning which I consider the proper anthropic principle is nonsensical to me. The fact that our universe does have observers certainly doesn't prove that parameter values excluding them were not possible.

The whole argument makes as much sense as arguing that since you rolled 6 on a dice only 6 was possible to begin with. Patently false."

No, the teleologically-tinged version of AP - whatever you think of it - is not the idea that things could not *logically* have been otherwise, such as to exclude observers (intelligent life, etc.) Of course (?) such life-unfriendly parameters are "possible" in purely logical terms or as we can imagine variations of physical law (not that we can get a handle on explaining that anyway, as I argued above.) Instead, the TAP (teleological AP) is suggesting (all anyone can do about this anyway) that there was a "purpose" behind things being this way - that the life friendly constants etc are there *in order to* make life come about.

You can complain there shouldn't be "anyone" out there to do that, or whatever; but it doesn't help to misunderstand the point of the TAP. In any case, I repeat: there is no way in logical principle to identify what possible world/s ought to "exist" more than as math itself. So we can either believe they all exist, or that for weird metaphysical reasons some PWs exist and some don't, or that "Someone" picked.

Neil, I mentioned (unfavorably) that interpretation in my previous post. But that version imo hardly qualifies as anthropic principle in the sense it is usually talked about in physics context, it's more a statement of religious faith then anything else and certainly doesn't qualify as a good explanation of anything either.

1. It isn't exclusively a principle of physics at all, but could also, and more effectively, I would think, be applied to Darwinian evolution. And when we do so we see the weakness, because it implies a teleological view of evolution of a sort that was discarded years ago as an embarrassment, and also discounted by Darwin himself. It implies that the whole point of evolution was to produce US, or at least those of us who ponder the meaning of evolution. In other words it implies that the only meaningful course for evolution to have taken was to produce those of us capable of theorizing about it.

2. It's fundamentally no different from solipsism, because the existence of "beings capable of examining the universe scientifically" can always be reduced to "myself," because if "I" never existed, then neither would the universe "as I know it." Solipsism is an interesting idea because there is no way to logically refute it. But at the same time it's a sterile idea, because if true, then one is wasting one's time trying to convince anyone else of its truth.

The statement is not ambiguous. It's case 1 that you mentioned. Case 2 that you list is ambiguous, for it uses the vague phrase "ended up" that I don't know what it means. I explained in my post why being trivially true is not necessarily uninteresting. In fact, your comments illustrate very nicely the very reason I wrote this post. Best,

SOCRATES: But if he always possessed this knowledge he would always have known; or if he has acquired the knowledge he could not have acquired it in this life, unless he has been taught geometry; for he may be made to do the same with all geometry and every other branch of knowledge. Now, has any one ever taught him all this? You must know about him, if, as you say, he was born and bred in your house.SEE:Meno by Plato

If you weren't taught, how would you know?

You know Bee it is as if you taking a tallying of all the things you been through in terms of your work blogging.

I noticed how the neuronal connections(links) are working very good now as you express the subjects you've come to be acquainted with. Your making connections.

So, as your resource in information grows, you in my view become much more precise in your thinking and knowledge.

Where would these other universes be in relation to ours? Is there a way to envision it?

Well, we live in three spatial dimensions: We move back and forth, up and down, left to right. And then there's time, so that's our four-dimensional universe. Another universe might be essentially right next to ours by going in another direction that's not one of those four. We might call it "another kind of sideways." See: Riddles of the Multiverse

I was surprised by your cartoon because of familiarity:)

At the heart of modern cosmology is a mystery: Why does our universe appear so exquisitely tuned to create the conditions necessary for life? In this tour de force tour of some of science's biggest new discoveries, Brian Greene shows how the mind-boggling idea of a multiverse may hold the answer to the riddle.

So while throwing out additional resources for consideration, I do show something very much inherent in the expressions of the universe as a question, are they mathematically endowed?:) as a means to interpret the architectural structures that we are talking about in reductionism. How much finer indeed then to assess our knowledge then to find we are always going back to where we started in the beginning?:)Where is that? You could almost say this is cyclical.

@Bee: In case 2 "ended up" means precisely the same thing as with dice roll which ends up being 6 after you roll it. In other words it means realizing one variant out of many possible outcomes.

But if you meant the first interpretation ("since we already know observers do exist the parameter values must be consistent with this fact") then I am afraid that variant of anthropic principle is indeed useless, and not only useless it is actively harmful, as it is a restatement of the obvious fact that our models have to be consistent with observations using fancy, obscure, loaded and ill-defined terms. Using the phrase "anthropic principle" for something as trivial and mundane is silly at best.

Also this version certainly doesn't explain any parameter values. If you win a game of dice where you have to roll 6 to win by rolling that 6 it doesn't mean that your victory somehow "explains" why out of all the possible rolls you actually got 6. All that can be said is that if we know that you won and in this game you only win by rolling 6 then we can deduce that you must have rolled 6. Completely different thing.

The fact that there are like, 5 different variant interpretations proves that nobody knows what the anthropic principle is.

The fact that *IT* could be anything from a selection effect that requires a multiverse, to a very strong "bio-oriented" cosmological principle that resolves fine tuning problems from first principles, proves that most everyone has "ill informed misconceptions".

I find that people who pretend to have a clue what the anthropic principle is usually don't really know all that much about that physics that defines it.

But I, personally would assert to anyone that actually has bothered to study the precariously, (top of the hill), balanced physics that creates all the problems, and the commonly balanced "goldilocks" features that make up our local *ecobalances*and "habitable zones", that it soon becomes obvious that the anthropic principle is very simply an energy conservation law that requires life as a **necessary** function of the thermodynamic process. A maximum action principle whose many precariously balanced commonalities reflect the same "flat" balanced feature as the universe itself, which is quite obviously configured to maximize work, since this structuring most certainly will enable the energy of the universe to dissipate MUCH more uniformly, over the maximum amount of time possible, than the wide-open useless dead inert energy of the universe that quantum theory derives without a suppression mechanism in effect that is constraining the forces to produce the energy efficient structure that is observed.

Course, recognition of this would people to give up their god, Copernicus, and that ain't about to happen.

One could, by the same token, ask: Why is the evolution of life-forms fine-tuned for today's physics?

Sorry, but this DOES sound like cause and effect. The so-called "anthropic principle" is really a principle that could be applied to any evolutionary process. It is fundamentally about evolution and not physics. It is also, just as fundamentally, a metaphysical problem and as such could never be settled through scientific research.

PTMR - again, I don't know if anyone is saying there is some reason "six" had to roll up unless there is something that makes it that way - of course it is not just a retro causation of it having turned out that way. That's the silly circular form of the argument, but you'd be surprised how many people still act like it's game. It's the universe/s themselves that need to be explained. Sure, if everything needed an explanation, then the ground or absolute or whatever would too, but presumably *something* has to be "self existent" to avoid infinite regress - and that should not be just some particular model world as I explained. You can be taken aback from it sounding like "God" (altho it's nature is not defined, simply the necessary logical role), but I repeat - there is no *logical* way to pick out PWs that "deserve to exist" from those that don't. It's either MUH/ultimate ensemble, or "someOne" does something about them. We can't get a purely rational handle on it anyway, take your pick. Not scientific? At the highest level, that just isn't available.

DocG: No, it isn't. As Barrow and Tipler well argued, it's the features of the laws and constants that make life even remotely possible. Change alpha etc too much and it's a very long shot to get any life. A vague sense that "something would adapt" to greatly different constants is an ironically unscientific article of faith (if such it is - unless you have an equally capable rebuttal to B&T et al.)

String theory predicts a large number of possible universes, called the "backgrounds" or "vacua." The set of these vacua is often called the "multiverse" or "anthropic landscape" or "string landscape." See: Anthropic principle

Hopefully one's seen how it worked into Brian Greene's Ted lecture. Maybe #1 needs a bit of a correction?

#1(part of):The reason it is often mentioned in combination with the multiverse is that proponents of the multiverse argue it is the only explanation, and no further explanation is needed or necessary to look for.

While demonstrating tendencies toward #1 without exaggerating some religious conviction or some reference to intelligent design, in that logic of string theory.....it just is?

Once there is "symmetry breaking" what is expressed in the valley? It then ties in with what Greene show's as a process of what is geometrically expressed and explore with regard to genus development? Not only as a number, but by it's tendency as well towards it shape?

The technical details, are constraint by how genus progress exists in those valleys, and as a definition and expression of, has been enhanced by how dark energy is expressed by the identification of that number.

In this context, it just is.

Just so you know, I am always open to correction. I do not know any other answer other then to show, the reference to string theory always existed?:)

PTMR, you have a point - yet ironically, I was myself criticizing others who may be pushing farther than warranted beyond "the limits of our knowledge." Sure, their speculations have a "basis" in physics, but are still not verifiable or provided by an utterly clear and accepted theoretical background. Note I wasn't even picking one specific claimed "right answer", but rather giving the logically plausible choices. Odd for you to refer to all that as giving a "wrong" answer, giving that it was neither a specific answer nor demonstrated false.

Plato - again, our being able to theorize some fundamental constituent like strings, doesn't mean that being able to "imagine" them working differently is equivalent to their being other such examples. Nor does it explain how they might change from one to the other. The laws behind the strings are in turn just "given" and not explained in terms of known deeper constituents (the way that real rubber bands are explained in terms of their molecular composition.) At the highest level they too remain inexplicable in ultimate existential terms.

Finally, if it's "wrong" to postulate something beyond worlds because we can't find it, then neither should MWI or even multiverse explanations be considered legitimate science unless and until we can "find" something to back them up.

I just don't have any other explanation so #1 precludes any other points that Bee raised.

Invalidates, any other misnomers?

The society and Bee tend to work from the position of, it is an aspect of intelligent design scenario and of course Susskind had to respond by writing his own book too.:)

While seeking clarity Bee just reveal much clearly what she always believed in the beginning with a small change as she writes," But it’s neither useless nor a tautology nor does it acknowledge that the universe can’t be explained from first principles.?)

Plato, you have some good points as did Bee et al. However I repeat: my main point was not to promote a specific answer, but it was to explain why we can't explain the universe "from first principles." We can't, because logical methods just can't go beyond the existence and structures of the models themselves. This is (ironically?) something that both some astute physicists like Tegmark, as well as some philosophical theists (not to be confused with "religion") agree on. Hence we can pick:1. There is an ultimate ensemble (not just a "string theory landscape" which is just another, albeit large, chunk of the PWs that need justifying.)2. "Something" above specific PWs makes for what exists, whatever it is - but it's not part of "logic", since the latter can't *analyze* somethign that is not a predicate.3. Either stop trying because it's beyond what PTMR calls "the limits of knowledge."4. Believe what you want to (and after all, the meta-philosophical criticisms of what we ought to believe or what is meaningful etc is about as woolly as what it tries to criticize.)

Note that we have no more evidence of many worlds, other universes, MUH etc than we do of "God" etc. (for which there may also be clever *arguments*), so let's have some consistency about what it's "OK" to believe.

Neil Bates: "As Barrow and Tipler well argued, it's the features of the laws and constants that make life even remotely possible. Change alpha etc too much and it's a very long shot to get any life."

But the same exact thing can be said with respect to the evolution of life forms. Most animals have mouths thanks to a mutation, or series of mutations, that must have taken place at least hundreds of millions of years ago. If that mutation (or any of those in the series) had never taken place, or if the line bearing the mutation had died out, then we would not have mouths today.

So it's hard for me to separate out the Anthropoic Principle from basic Darwinian evolution. Every single thing we see today is the result of highly improbable events in the past. The operant term is: contingency.

DocG: Maybe, but Barrow and Tipler and similar argue at a *very* basic level. I suggest (re?)familiarizing yourself with their arguments as they are, before developing great confidence in an easy alternative.

BTW "craptcha" has been denying several "obvious" correct transcriptions lately ... but at least I can comment at all - some odd thing with settings kept me away for months.

PS, ^^ I should have just said that quite a few "philosophers" overall (notable e.g. David Lewis) agree or agreed that we can't use logical methods to find what ought to "exist" (or in some cases, other than a fundamental "necessary being") - not necessarily because it helps advance some agenda. Many of them just say what needs saying.

Sorry, apologies to PTMR who did write "wrong answers" - presumably meaning the entire class of such speculations is unwarranted or futile etc. (even if "wrong" is the wrong choice of word), which is a game point. My other points stand.

The Cosmic Landscape: String Theory and the Illusion of Intelligent Design is Susskind's first popular science book, published by Little, Brown and Company on December 12, 2005.[23] It is Susskind's attempt to bring his idea of the anthropic landscape of string theory to the general public. In the book, Susskind describes how the string theory landscape was an almost inevitable consequence of several factors, one of which was Steven Weinberg's prediction of the cosmological constant in 1987. The question addressed here is why our universe is fine-tuned for our existence. Susskind explains that Weinberg calculated that if the cosmological constant was just a little different, our universe would cease to exist.

The logic has not ended, but revealed that such extensions to the #1 reveals that there is a continuance of this subject, wile it still retains the functionality of the parameters Anthropic Landscape that has been given too Intelligent design according historical connotations. By Bee.

As I said, such extensions have been revealed not only in Bee's thoughts, but in the recognition of #1. That is not wishful thinking but set in the prospects of intelligent conversation(not intelligent design) as to what Greene reveals in the Ted lecture. Susskind as well, spoke to this.

Some discussion of strong vs weak anthropic principles in the comments, but I'm surprised this wasn't listed among the misconceptions, because it certainly ranks as one.

The authentic distinction seems to be that the weak anthropic principle is that we shouldn't conclude more than is warranted from the fact of our own existence (in particular, that it needn't be a great mystery why we find ourselves in a world conductive to life, since it is not logically consistent to find ourselves NOT so), whereas the strong anthropic principle is the hypothesis that reality actually IS constrained in some way to be conductive to life.

However, some authors have used completely different definitions, in which BOTH the weak and strong anthropic principle are variations on the idea that we shouldn't conclude more than is warranted from the fact of our own existence, and the ONLY difference between them is that the strong anthropic principle supposes multiple universes, whereas the weak anthropic principle applies within a single universe. By this definition, the strong anthropic principle addresses "Why is the universe just right?", whereas the weak anthropic principle addresses "Why is the solar system just right?".

You will find these definitions in Penrose (Emperor's New Mind, 1990 printing, chapter 10), and I've also seen it in a book by Davies.

This is obviously important, because the version most often discussed is the WEAK anthropic principle by the former set of definitions and the STRONG anthropic principle by the latter.